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1.
水体生态环境中的微塑料与重金属污染问题正日益受到热切关注为探讨微塑料与重金属对水产品的复合生态效应,选择鄱阳湖饶河段优势淡水鱼为研究对象,对鱼体内微塑料及重金属Cu、Cd、Pb、Zn、Cr等元素的生物累积作用进行分析与评价结果表明:调查区域水环境中微塑料的丰度范围10～64 items/L,平均值38.56 items/L. 8种淡水鱼消化道微塑料丰度范围为1.21～9.11 items/g,平均丰度为5.40 items/g;鳃部丰度范围0.61～5.00 items/g,平均丰度为2.87 items/g;微塑料类型主要有碎片类、纤维类、薄膜类和颗粒类4种,其聚合物成分主要为聚乙烯(PE)、低密度聚乙烯(LDPE)、聚丙烯(PP)和聚苯乙烯(PS);颜色以透明及彩色为主;微塑料粒径范围为0.01～9.5 mm,粒径0.5 mm的微塑料所占比例为79.07%,鱼体内与其生存水环境中微塑料的丰度特征(形态、粒径、颜色和聚合物类型组分比例)具有一定相似性各鱼类对微塑料的累积系数(BAF)平均值为178.29,不同鱼类累积微塑料的能力大小次序为:乌鳢(Channa argus)、黄颡鱼(Pelteobagrus fulvidraco)鲦鱼(Hemicculter leuciclus)、草鱼(Ctenopharyngodon idellus)、鲶鱼(Silurus asotus)鲤鱼(Cyprinus carpio)、刀鱼(Coilia ectenes)、鲫鱼(Carassius auratus)鱼体肌肉组织内重金属Cu、Cd、Pb、Zn、Cr的平均含量分别为4.27、0.13、0.28、11.73、0.53 mg/kg,均符合无公害水产品的要求且低于人体消费卫生标准,属于安全食用范围;鱼类对5种不同重金属的累积能力大小次序为ZnCuCdPbCr,不同鱼类对不同重金属的累积能力具有差异性通过扫描电镜(SEM)与能谱分析(EDS)检测到各类型微塑料表面均有上述5种重金属元素,证实微塑料可能成为重金属的附着载体,相关性分析表明微塑料与Cu呈极显著相关,与Cd、Pb均呈显著相关;微塑料的存在一定程度上会增强Cu、Cd与Pb的累积效应,并可能产生复合污染效应.  相似文献   

2.
枝角类体内氮磷比与生活史策略的选择密切相关,大型枝角类通常体内含磷量高、个体生长快、生殖率高,而小型枝角类体内含磷量低,个体生长相对较慢、生殖率低.由于大型枝角类对磷的需求比较高,我们假设大型枝角类生活史各参数对食物磷缺乏比小型枝角类更为敏感.本研究比较分析了食物碳磷比对流溪河水库两种枝角类（盔型溞（Daphnia galeata）和脆弱象鼻溞（Bosmina fatalis））生活史各参数的影响.实验设计了3个食物质量处理组：高磷（碳：磷=105）、中磷（400）和低磷（1450）,食物浓度均为2 mg C/L的蛋白核小球藻（Chlorella pyrenoidosa）.脆弱象鼻溞内禀增长率、幼溞生长速率、平均每窝产仔量和首次生殖时体长均随着食物碳磷比的升高而显著下降;首次生殖时间则随着食物碳磷比的升高而显著延长;新生幼溞体长在各食物处理中无显著差异.盔型溞幼溞生长速率、平均每窝产仔量和首次生殖时体长均随着食物碳磷比的升高而显著下降;内禀增长率和新生幼溞体长在高磷处理组显著高于中磷和低磷处理组,但在中磷和低磷处理组无显著差异;首次生殖时间在高磷处理组显著短于中磷和低磷处理组,但在中磷和低磷处理组无显著差异.结果表明,食物的磷缺乏降低了两种枝角类的内禀增长率和幼溞生长速率,并延长了性成熟时间;盔型溞的内禀增长率、首次生殖时间和平均每窝产仔量等生活史参数受食物磷限制的程度小于脆弱象鼻溞,导致盔型溞对脆弱象鼻溞有竞争优势.  相似文献   

3.
Plastic debris is known to undergo fragmentation at sea, which leads to the formation of microscopic particles of plastic; the so called ‘microplastics’. Due to their buoyant and persistent properties, these microplastics have the potential to become widely dispersed in the marine environment through hydrodynamic processes and ocean currents. In this study, the occurrence and distribution of microplastics was investigated in Belgian marine sediments from different locations (coastal harbours, beaches and sublittoral areas).Particles were found in large numbers in all samples, showing the wide distribution of microplastics in Belgian coastal waters. The highest concentrations were found in the harbours where total microplastic concentrations of up to 390 particles kg−1 dry sediment were observed, which is 15-50 times higher than reported maximum concentrations of other, similar study areas.The depth profile of sediment cores suggested that microplastic concentrations on the beaches reflect the global plastic production increase.  相似文献   

4.
Cataclasis and processes of particle size reduction   总被引：6，自引：0，他引：6  
The particle size distribution (P.S.D.) of fragmented geological materials is affected by the fragmentation process, initial size distribution, number of fracturing events, energy input, strain, and confining pressure. A summary of literature shows that the fractal dimension (D) of the P.S.D. is increased by the number of fracturing events, energy input, strain, and confining pressure. Cenozoic cataclasis of granite, granodiorites, gneisses and arkose seen in cores from the Cajon Pass drillhole, southern California, produced P.S.D.s with values ofD that varied from 1.88 to 3.08. Each rock type has a characteristic and more limited range ofD. Areas of dilatant texture and modeI fracture-fillings have low average values (2.32 and 2.37) compared to an average value of 2.67 in shear fracture-fillingsD has a good inverse correlation with average particle size. Data from fault rocks in the San Gabriel fault zone, southern California (Anderson et al., 1983) have been reanalyzed to show that values ofD are higher (2.10–5.52) and average particle size is lower than the Cajon Pass samples, but the ranges of values overlap, and the inverse correlation betweenD and average particle size is extended. Microstructural observations combined with these results suggest that three processes contributed to particle size reduction during cataclasis. The first process of feldspar alteration, which leads to low values ofD, has not been previously recognized. The second process is probably constrained comminution (Sammis et al., 1987), since the averageD in shear fracture-fillings is close to the value of 2.58 predicted by this theory. A further stage of particle size reduction is demonstrated by an increase ofD with cataclasis. This third process is selective fracture of larger particles, which may also operate during localization and the cataclastic flow-to-faulting transition as observed in experiments. A transition from constrained comminution to selective fracture of large particles, and increasingD values with cataclastic evolution and grain size reduction, may be general features of experimental and natural cataclasis.  相似文献   

5.
微塑料作为新型环境污染物正日益受到人们密切关注,为探索微塑料在鄱阳湖流域的污染状况,以鄱阳湖流域"五河"入湖口的沉积物为研究对象,分别在3个水文周期（平水期、丰水期和枯水期）选择6个典型区域采集沉积物进行分析.采用浮选分离方法及金相显微鉴定技术,分析鄱阳湖"五河"入湖口沉积物中微塑料的类型、丰度和表面形貌等特征,旨在揭示鄱阳湖沉积物中微塑料的空间分布规律及不同水位期的动态变化.研究结果显示微塑料的类型有碎片类、发泡类、薄膜类和纤维类,其中主要以碎片类微塑料为主,所占百分比为51.95%;70%的微塑料粒径<1 mm,微塑料（<5 mm）的平均丰度为811.11 n/kg,6个样点的微塑料丰度值表现为朱港 > 吴城 > 渡头乡 > 龙口 > 瑞洪镇 > 南矶山.6个样点的微塑料丰度值与鄱阳湖水位动态均具一致性,在枯水期所占比例最高,达到44.41%;平水期次之,达到31.52%;丰水期所占比例最低,仅占24.07%.不同水期、不同样地存在不同程度的微塑料污染问题警示人们要重视塑料垃圾的排放及其污染问题,以减少对湖泊、河流等湿地生态环境的影响.  相似文献   

6.
Aliphatic hydrocarbons and PAHs in the whole soft tissues of Bathymodiolus azoricus from three Mid-Atlantic Ridge hydrothermal vents (Menez-Gwen, Lucky Strike and Rainbow), and Mytilus galloprovincialis from three contaminated coastal sites in South Portugal were analysed, and its effects on the digestive gland microsomes mixed-function oxygenase system (MFO) were assessed.Aliphatic hydrocarbons levels were present in the same magnitude in both coastal and hydrothermal environments, while the UCM (unresolved complex mixture) for coastal mussels were higher than in vent mussels. In general, significantly higher PAHs concentrations were found in coastal mussels, compared to B. azoricus where low molecular weight PAHs (2–3 rings) represented the majority of PAHs contrarily to what was observed in M. galloprovincialis. The MFO components were present in both mussel species, and were detected in vent mussels for the first time. However this system seems to have different roles in species from these contrasting environments. In coastal mussels MFO responded to hydrocarbon contamination while response in hydrothermal organisms appeared to be related mainly to endogenous factors.  相似文献   

7.
秦镕聪  肖艳  郭劲松  李哲  方芳  刘静  杨梅 《湖泊科学》2018,30(5):1284-1294
本文通过选取水华鱼腥藻(Anabaena flos-aquae)、铜绿微囊藻(Microcystis aeruginosa)、空球藻(Eudorina sp.)和湖北小环藻(Cyclotella hubeiana)为三峡库区流域中典型的优势藻,在澎溪河进行原位培养试验,跟踪监测了三峡水库不同运行时期4种典型优势藻细胞氮(Cell-N)、磷(Cell-P)浓度以及环境水体中的总氮(TN)、总磷(TP)浓度,并且结合团队之前的研究成果,根据临界(供应)N/P摩尔比、细胞N/P摩尔比和Guildford的TN/TP摩尔比评价标准对库区水体的营养限制状态进行了评价,为进一步揭示三峡水库运行下支流水域富营养化过程与生理特征的限制性评价提供研究基础.原位试验结果表明:3个评价标准下水体的营养(氮或磷)限制状态基本相同,低水位时期水体无机磷营养盐比较贫乏,在试验初期没有显著的营养盐限制而在末期受到了磷的相对限制;高水位试验初期和末期均未呈现显著的营养盐限制;泄水期营养盐变动频繁,试验初期表现为氮限制而末期表现为磷限制.虽然各藻种在不同时期会表现出不同的营养盐限制性,但总的来看,临界N/P比和细胞N/P比的阈值范围具有一定指示作用,能够从藻类细胞生理的角度对水体的营养状况作出初步评价.  相似文献   

8.
The effects of wind-driven rain (WDR) on sand detachment were studied under various raindrop obliquities. Results suggested a significant reduction in compressive stress on sand surfaces for a two-dimensional experimental set-up in a wind tunnel. During experiments, sand particles in splash cups were exposed to both wind-free rain (WFR) and WDR driven by horizontal winds of 6.4, 8.9 and 12.8 m s−1 and rainfall intensities of 50, 60, 75 and 90-mm h−1 to assess the sand detachment rate (D, in g m−2 s−1). The effects of sand moisture state (dry and wet) on the detachment of different-sized particles (0.20–0.50 and 0.50–2.00 mm, respectively) were also tested. Factorial analysis of variance showed that shear and compressive stress components evaluated by horizontal and vertical kinetic energy flux terms (KEx and KEy, respectively, in J m−2 s−1) along with their vector sum (KEr, in J m−2 s−1) explained the variation in D. Neither sand size nor sand moisture was statistically significant alone although binary interactions of KEr, KEx and KEy with the sand size and three-way interaction of KEx, sand size and moisture were statistically significant. These results can be explained by size-dependent variation in sand compressibility and surface friction related to the total stress field developed by a given partition of shear and compressive stresses of wind-driven oblique raindrops (KEx/KEy). Further analysis of the variation of the unit sand detachment rate (Du = D/KEr = g J−1) with rain inclination (α, in degrees) better revealed the effect of WDR obliquity on Du that further changed with sand size class and moisture state. Finally, the difference in the resulting stress field differentiable by the oblique raindrop trajectories of the experiment over sand surface significantly affected the non-cohesive particle detachment rates, to some extent interacted with size-dependent compressibility and interface shear strength of sand grains.  相似文献   

9.
The composition and grain size characteristics of sediment in estuarine and coastal environments provide important information on the material source, hydrodynamic environment, environmental events,etc. However, few studies have focused on the sediment characteristics of the entire Qiantang Estuary,particularly, on the correlation between hydrodynamics and sediment properties. Through systematic sampling of the surface sediment in a large area of the Qiantang Estuary, the spatial distribution ch...  相似文献   

10.
Increased sediment loads from accelerated catchment erosion significantly degrade waterways worldwide. In the South East Queensland region of Australia, sediment loads are degrading Moreton Bay, a Ramsar listed wetland of international significance. In this region, like most parts of coastal Australia, sediment is predominantly derived from gully and channel bank erosion processes. A novel approach is presented that uses carbon and nitrogen stable isotope ratios and elemental composition to discriminate between these often indistinguishable subsoil sediment sources. The conservativeness of these sediment properties is first tested by examining the effect of particle size separation (testing for consistency during transport) and the effect of sampling at different times (testing for temporal source consistency). The discrimination potential of these sediment properties is then assessed with the conservative properties, based on the particle size and temporal analyses, modelled to determine sediment provenance in three catchments. Nitrogen sediment properties were found to have significant particle size enrichment and high temporal variance indicative of non‐conservative behaviour. Conversely, carbon stable isotopes had very limited particle size and temporal variability highlighting their suitability for sediment tracing. Channel erosion was modelled to be a significant source of sediment (μ 51%, σ 9%) contrasting desktop modelling research that estimated gully erosion is the predominant sediment source. To limit the supply of sediment to Moreton Bay, channel bank and gully erosion must both be targeted by sediment management programs. By distinguishing between subsoil sediment sources, this approach has the potential to enhance the management of sediment loads degrading waterways worldwide. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

11.
Sewage effluent input and population were chosen as predictors of microplastic presence in sediments at four sites in the River Thames basin (UK). Large microplastic particles (1 mm–4 mm) were extracted using a stepwise approach to include visual extraction, flotation and identification using Raman spectroscopy. Microplastics were found at all four sites. One site had significantly higher numbers of microplastics than other sites, average 66 particles 100 g? 1, 91% of which were fragments. This site was downstream of a storm drain outfall receiving urban runoff; many of the fragments at this site were determined to be derived of thermoplastic road-surface marking paints. At the remaining three sites, fibres were the dominant particle type. The most common polymers identified included polypropylene, polyester and polyarylsulphone. This study describes two major new findings: presence of microplastic particles in a UK freshwater system and identification of road marking paints as a source of microplastics.

Capsule

This study is the first to quantify microplastics of any size in river sediments in the UK and links their presence to terrestrial sources including sewage and road marking paints.  相似文献   

12.
Fluvial suspended sediment typically consists of a variety of complex, composite particles referred to as flocs. Floc characteristics are determined by factors such as the source, size and geochemical properties of the primary particles, chemical and biological coagulation processes in the water column and shear stress and turbulence levels in the stream. Studies of floc morphology have used two contrasting methods of sampling and analysis. In the first method, particles settle on a microscope slide and are observed from below using an inverted microscope. The second method uses filtration at no or low vacuum and particles deposited on the filter are observed with a microscope. Floc morphology can be quantified using fractal dimensions. The aims of the present study were to examine the effect of the two sampling methods on the fractal dimensions of particle populations, and to evaluate for each method how well the fractal dimensions at the various sampling sites reflect basin conditions. Suspended solids were collected in triplicate on inverted microscope slides and on 0·45 μm Millipore HA filters in two southern Ontario streams with contrasting riparian zones during a minor runoff event resulting from the melt of a freshly fallen snowpack. An image analysis system was used to determine area, longest axis and perimeter of particles. The morphology of the particle population of each sample was characterized using four fractal dimensions (D, D1, D2 and DK). Systematic differences in fractal dimensions obtained with the two methods were observed. For the settling method, outlines of larger particles were frequently blurred because of the distance between the focal plane (the top of the inverted microscope slides) and the plane of the particle outline. In this method, the blurring of large particles can cause an increase in the projected area and length of the particle. The effect on the particle perimeter is unpredictable because it depends on the amount of detail lost through blurring and its effect on the apparent increase in particle size. Because of blurring, D and D1 tend to be systematically lower for the settling method, whereas the net effect on D2 is unpredictable. Particle size distributions derived from settling are typically coarser because small, low density particles may remain in the water column and all particles may not deposit on the slides. This loss of fines results in systematically lower DK values for the settling method compared with the filtration method. Fractal dimensions and particle size distributions obtained with the filtration method were sensitive to and clearly indicated differences between drainage basins and between sites within each basin. These differences were explained by basin characteristics and conditions. Fractal dimensions and particle size distributions obtained with the settling method were less sensitive to drainage basin characteristics and conditions, which limits their usefulness as process indicators. Copyright © 1999 John Wiley & Sons, Ltd.  相似文献   

13.
Phytoplankton size structure plays a significant role in controlling the carbon flux of marine pelagic ecosystems. The mesoscale distribution and seasonal variation of total and size-fractionated phytoplankton biomass in surface waters, as measured by chlorophyll a (Chl a), was studied in the Southern Yellow Sea using data from four cruises during 2006–2007. The distribution of Chl a showed a high degree of spatial and temporal variation in the study area. Chl a concentrations were relatively high in the summer and autumn, with a mean of 1.42 and 1.27 mg m−3, respectively. Conversely, in the winter and spring, the average Chl a levels were only 0.98 and 0.99 mg m−3. Total Chl a showed a clear decreasing gradient from coastal areas to the open sea in the summer, autumn and winter cruises. Patches of high Chl a were observed in the central part of the Southern Yellow Sea in the spring due to the onset of the phytoplankton bloom. The eutrophic coastal waters contributed at least 68% of the total phytoplankton biomass in the surface layer. Picophytoplankton showed a consistent and absolute dominance in the central region of the Southern Yellow Sea (>40%) in all of the cruises, while the proportion of microphytoplankton was the highest in coastal waters. The relative proportions of pico- and nanophytoplankton decreased with total biomass, whereas the proportion of the micro-fraction increased with total biomass. Relationships between phytoplankton biomass and environmental factors were also analysed. The results showed that the onset of the spring bloom was highly dependent on water column stability. Phytoplankton growth was limited by nutrient availability in the summer due to the strong thermocline. The combined effects of P-limitation and vertical mixing in the autumn restrained the further increase of phytoplankton biomass in the surface layer. The low phytoplankton biomass in winter was caused by vertical dispersion due to intense mixing. Compared with the availability of nutrients, temperature did not seem to cause direct effects on phytoplankton biomass and its size structure. Although interactions of many different environmental factors affected phytoplankton distributions, hydrodynamic conditions seemed to be the dominant factor. Phytoplankton size structure was determined mainly by the size-differential capacity in acquiring resource. Short time scale events, such as the spring bloom and the extension of Yangtze River plume, can have substantial influences, both on the total Chl a concentration and on the size structure of the phytoplankton.  相似文献   

14.
The paper presents the results of field measurements of critical conditions for bedload motion conducted in the Rio Cordon, a steep boulder‐bed stream in the Italian Alps, under conditions of high Reynolds numbers and low relative submergence poorly explored before. Two methods have been used to determine threshold of motion: the displacement of marked clasts and the flow competence approach, which uses the largest grain size diameter transported by each flood event. The high values of confirm the great relevance of non‐bedload effective shear stresses in step–pool streams given by the additional form drag associated with this morphology. Relative submergence effects on the dimensionless critical shear stress have been quantified by considering the relative submergence ratio Rh/D84, and the major effect of relative size on the mobility of each particle in steep, widely graded bed mixtures has been evaluated. Finally, the dimensionless critical unit discharge has also been adopted in the regression equations as the critical hydraulic parameter, because it may represent an easier parameter to use than the critical shear stress for steep, rough mountain rivers. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

15.
Laboratory experiments using simulated tilting rill channels with different bed roughnesses have been conducted to determine hydraulic conditions for incipient motion of single rock fragments lying on rill beds. These threshold conditions can be described by a modified Shields' entrainment parameter (θm) and relative depth (Z), adjusted for rill conditions. The negative relation found between θm and Z also fits steep (stream) channel data collected by other investigators. Plots of the classical Shields' entrainment parameter (θ) versus both relative depth and relative particle size also showed clear negative trends. Special care has been taken to avoid false relations that can arise between compound parameters. This occurs when the latter are not independent from each other because of their definitions.  相似文献   

16.
Microplastics have been recently identified as marine pollutants of significant concern due to their persistence, ubiquity and potential to act as vectors for the transfer and exposure of persistent organic pollutants to marine organisms. This study documents, for the first time, the presence and abundance of microplastics (>1.6 microm) in Singapore's coastal environment. An optimized sampling protocol for the collection and analysis of microplastics was developed, and beach sediments and seawater (surface microlayer and subsurface layer) samples were collected from nine different locations around the coastline. Low density microplastics were separated from sediments by flotation and polymer types were identified using Fourier transform infrared (FTIR) spectrometry. Synthetic polymer microplastics identified in beach sediments included polyethylene, polypropylene, polystyrene, nylon, polyvinyl alcohol and acrylonitrile butadiene styrene. Microplastics were detected in samples from four out of seven beach environments, with the greatest quantity found in sediments from two popular beaches in the eastern part of Singapore. Polyethylene, polypropylene and polystyrene microplastics were also found in the surface microlayer (50-60 microm) and subsurface layer (1m) of coastal waters. The presence of microplastics in sediments and seawater is likely due to on-going waste disposal practices from industries and recreational activities, and discharge from shipping.  相似文献   

17.
We investigate a new proxy for ENSO climate variability based on particle‐size data from long‐term, coastal sediment records preserved in a barrier estuary setting. Corresponding ~4–8 year periodicities identified from Wavelet analysis of particle‐size data from Pescadero Marsh in Central Coast California and rainfall data from San Francisco reflect established ENSO periodicity, as further evidenced in the Multivariate ENSO Index (MEI), and thus confirms an important ENSO control on both precipitation and barrier regime variability. Despite the fact that barrier estuary mean particle size is influenced by coastal erosion, precipitation and streamflow, balanced against barrier morphology and volume, it is encouraging that considerable correspondence can also be observed in the time series of MEI, regional rainfall and site‐based mean particle size over the period 1871–2008. This correspondence is, however, weakened after c.1970 by temporal variation in sedimentation rate and event‐based deposition. These confounding effects are more likely when: (i) accommodation space may be a limiting factor; and (ii) particularly strong El Niños, e.g. 1982/1983 and 1997/1998, deposit discrete >cm‐thick units during winter storms. The efficacy of the sediment record of climate variability appears not to be compromised by location within the back‐barrier setting, but it is limited to those El Niños that lead to barrier breakdown. For wider application of this particle size index of ENSO variability, it is important to establish a well‐resolved chronology and to sample the record at the appropriate interval to characterize deposition at a sub‐annual scale. Further, the sample site must be selected to limit the influence of decreasing accommodation space through time (infilling) and event‐based deposition. It is concluded that particle‐size data from back‐barrier sediment records have proven potential for preserving evidence of sub‐decadal climate variability, allowing researchers to explore temporal and spatial patterns in phenomena such as ENSO. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

18.
以湖北保安湖为研究对象,分别于2021年4、7、10月和2022年1月采集表层水样,测定水体中微塑料丰度、粒径、形状、颜色和类型,探究浅水型湖泊表层水体中微塑料的时空分布特征及其影响因素。结果表明,保安湖表层水体微塑料的年平均丰度为(16.20±2.23)items/L。微塑料丰度呈现明显的季节性差异,其中夏季(采样时间7月)平均丰度最低,为(1.40±0.09)items/L。在所有微塑料颗粒中,粒径0.064～1 mm占比最大,为82.57%;黑色和无色微塑料占主导地位,占比分别为36.16%和21.31%;纤维状微塑料分布最广泛,占比达40.01%;聚乙烯(PE)和低密度聚乙烯(LDPE)是最主要的微塑料类型,两者之和占比达46.05%,其次为聚苯乙烯(PS,占比17.2%)、聚对苯二甲酸乙二醇酯(PET,占比8.33%)和聚乙酸乙酯(PVAC,占比8.31%)。统计分析表明,微塑料丰度与湖水水质无显著相关关系。该研究揭示了长江中下游地区典型浅水湖泊微塑料分布现状,为评估类似湖泊微塑料潜在污染风险提供了科学依据。  相似文献   

19.
The study of the coastal landscapes of hotspot oceanic islands through comprehensive structural metrics and ecological estimators represents an opportunity to explore geomorphological transformations and broad spatiotemporal scale features of coastal evolution. As part of this approach, a new metrical comparative analysis is presented in this study, comprising four islands in different evolutionary stages. They belong to the Cape Verde archipelago, which forms a double insular chain in which an east–west gradient in age and evolution is particularly evident across the southern chain. A space-for-time (SFT) substitution approach is applied to the coasts of (1) Fogo, in the shield stage; (2) Santiago, in the early post-erosional stage; (3) São Vicente, in the advanced post-erosional stage; and (4) Boa Vista, in the last erosional stage. From the obtained spatial distributions and frequencies of landforms, the coastal landscapes of these islands are compared in relation to their (i) geomorphic composition, using similarity indices (Whittaker, βw, Sorensen, Cs) and nestedness estimators (NOFD, WNODF), (ii) geomorphic abundance, using morpho-assembling densities (Dgm), and (iii) geomorphic diversity, using six alpha-diversity indices (Richness, S, Menhinick, DMN, Simpson, D, Shannon, H', Berger-Parker, d, and Brillouin, HB). An advanced geomorphological taxonomy is implemented for areas with limited open-access data, including a set of planform features captured through scale-frequency decomposition. Photographic, cartographic and fieldwork data are used for landform identification at 1200 random sampling points, empirically determined by a bootstrap method. The results show a chronological ordering of the compared variables and a possible co-evolution towards an increase in organizational geomorphic complexity of coastal systems at broad space-timescales. The method proposed in this study can contribute, from a metrical perspective, to finding new long-term evolutionary features and constitutes an advance in the development of an integrated model of coastal evolution in oceanic islands. © 2019 John Wiley & Sons, Ltd.  相似文献   

20.
为探究重污染底泥对沉水植物繁殖体萌发和幼苗生长影响,以苦草（Vallisneria natans）种子和黑藻（Hydrilla verticillata）冬芽为研究对象,以轻污染底泥为对照组,通过室内模拟实验研究了重污染底泥对两种繁殖体萌发和幼苗生长、生理特性的影响。实验结果表明,与轻污染底泥相比,重污染底泥对苦草种子萌发和幼苗生长无显著影响。黑藻冬芽萌发和幼苗地上部生物量在两组间没有显著差异,但重污染底泥组幼苗的地下部生物量显著高于轻污染底泥组,其地上部和地下部生物量比值由7.06±0.38下降至2.97±0.08。此外,苦草和黑藻幼苗受到重污染底泥胁迫表现出不同的生理响应。苦草幼苗叶片的类胡萝卜素含量显著减少,可溶性糖和蛋白含量分别降低11.56%、24.10%,根系活力也明显受到抑制,仅为（34.93±3.28） mg/（g·h）;黑藻幼苗生理响应与苦草略有不同,其叶片的叶绿素a、b含量显著增加,根系活力降低44.29%,可溶性糖和蛋白含量在轻污染组和重污染组之间无显著差异。由此可见,重污染底泥对苦草种子和黑藻冬芽的萌发影响不显著,但会明显影响幼苗的生长发育和生理特性,研究结果为...  相似文献   

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